The Flora of Disko Island and Adjacent Coast of West Greenland. 127 



exist some rather narrow-leaved specimens of L. groenlandiciim and some 

 broad-leaved ones of L. decumheris. In those cases, however, the absolute 

 size of the leaves will be decisive as L. groenlandiciim is moreover 

 a more large-leaved form. 



By comparing the lists I and II \ve see that the scanty material 

 of L. deciimbens from Arctic America and Siberia agrees very well with 

 the large one investigated from Greenland. The size and the shape 

 of the leaves are nearly the same. And by comparing the lists III 

 and IV, it will be seen that L. groenlandiciim from Boreal America has 

 somewhat larger leaves than the Greenland specimens, but 

 the shape is the same. The American piants belong to the same 

 stock, but where growing under more favourable circumstances, they are 

 better developed. 



The next question is: C an the plant here cailed L. deciimbens 

 by the size and shape of the leaves be distinguished from 

 L. palustre of Boreal Europe? By comparing the lists I and II with 

 V we see, that as to the size there is a wide difference: the leaves of 

 L. palustre are on an average twiceas longas those ofL. deciimbens. 

 As to shape there seems to be a shght difference too: the leaves of 

 L. palustre are also relatively somewhat longer than those of L. deciim- 

 bens^ (Comp. I and V). But as the leaves of piants ranging from boreal 

 zones into the arctic ordinarily become smaller, the size of the leaves 

 alone would hardly suffice to establish an independent species. 



According to our experience gleaned from the various parts of 

 West Greenland, L. deciimbens also varies, according to the conditions 

 of the habitat, developing rather large leaves in favourable situations. 

 Numerous examples will be found in the list I. And, on the other hånd, 

 it will be evident from examples in the list V that also L. palustre^ 

 under unfavourable conditions, varies inversely, leaves growing smaller. 

 However, even under extreme conditions, the two species will retain a 

 certain habit of their own, hardly to be described. After having closed 

 my investigation of the whole material I should easily at a glance be 

 able to match the different mounted specimens of L. deciimbens and 

 L. palustre without reading their labels. 



What is f. dilatata Wahl? 



In his Flora Lapponica W AULEi^iBERG mentions under Ledum pa- 

 lustre a |3 dilatatum: "foliis oblongo-ovahbus." Of this form 1 have seen 



the following specimens: 



N 1 b l/b 



Sweden, Falun, Hartman 6 27 7.6 3.55 



Japan, Nippon, Tchechonoski 5 27.5 6.0 4.58 



Lapland, Karesuando, Låstadius 6 40.0 5.8 6.90 



